This spectacular "blue marble" image is the most detailed
true-color image of the entire Earth to date. Using a
collection of satellite-based observations, scientists and
visualizers stitched together months of observations of the
land surface, oceans, sea ice, and clouds into a seamless,
true-color mosaic of every square kilometer (.386 square
mile) of our planet.

Much of the information contained in this image came from a
single remote-sensing device-NASA’s Moderate Resolution
Imaging Spectroradiometer, or MODIS. Flying over 700 km above
the Earth onboard the Terra satellite, MODIS provides an
integrated tool for observing a variety of terrestrial,
oceanic, and atmospheric features of the Earth. The land and
coastal ocean portions of these images are based on surface
observations collected from June through September 2001 and
combined, or composited, every eight days to compensate for
clouds that might block the sensor’s view of the surface on
any single day. Two different types of ocean data were used
in these images: shallow water true color data, and global
ocean color (or chlorophyll) data. Topographic shading is
based on the GTOPO 30 elevation dataset compiled by the U.S.
Geological Survey’s EROS Data Center. MODIS observations of
polar sea ice were combined with observations of Antarctica
made by the National Oceanic and Atmospheric Administration’s
AVHRR sensor the Advanced Very High Resolution Radiometer.
The cloud image is a composite of two days of imagery
collected in visible light wavelengths and a third day of
thermal infra-red imagery over the poles.